This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This study will utilize positron emission tomography imaging to assess the relationship between rapid eye movement behavior disorder (RBD) and Parkinson's disease (PD). Specifically, we will measure changes in brain function over time in patients with RBD to assess whether these patients are likely to go on to develop PD.